Hi
I have also seen this problem on GKI kernel [1]. They are for instance
built with clang, might have an impact. So the 'nr_swapper_spaces'
appear to be optimized out. Probably because of change [2].
I made a change to try handle the case, patch attached.
Regards
Johan
- [1] https://source.android.com/docs/core/architecture/kernel/gki-android13-5_15-release-builds
- [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b6038942480e574c697ea1a80019bbe586c1d654
________________________________________
From: 薛国伦 <xueguolun@xxxxxxxxxx>
Sent: Friday, 1 December 2023 09:07
To: HAGIO KAZUHITO(萩尾 一仁); devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Lianbo Jiang
Subject: [Crash-utility] Re: [External Mail]Re: [BUG FIXED]fix bug of CACHED in kmem -i show memory
Hi kazu: 1. I know that kernel have nr_swapper_spaces since kernel 4. 11 which brought into kernel with struct address_space *swapper_spaces[] my team think GKI vmlinux did not have nr_swapper_spaces this symbol, may due to compile rule changed
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Hi kazu:
1. I know that kernel have nr_swapper_spaces since kernel 4.11 which brought into kernel with struct address_space *swapper_spaces[]
my team think GKI vmlinux did not have nr_swapper_spaces this symbol, may due to compile rule changed in AOSP code.
we will try to find the root cause of vmlinux without symbol name nr_swappera_space.
>> RELEASE: 6.1.25-android14-11-maybe-dirty-qki-consolidate
>> crash> nr_swapper_spaces
>> crash: command not found: nr_swapper_spaces
2. I printf log of crash when execute kmem -i, it run into branch of "symbol_exists("swapper_spaces")", also can not find nr_swapper_spaces
if (symbol_exists("nr_swapper_spaces") {
......
} else if (symbol_exists("swapper_spaces") {
......
} else if (symbol_exists("swapper_space") {
......
}
3. using my patch, it can fix output log of kmem -i which CACHED show not right.
Fix before:
crash> kmem -i
PAGES TOTAL PERCENTAGE
TOTAL MEM 2854115 10.9 GB ----
FREE 169699 662.9 MB 5% of TOTAL MEM
USED 2684416 10.2 GB 94% of TOTAL MEM
SHARED 891094 3.4 GB 31% of TOTAL MEM
BUFFERS 329 1.3 MB 0% of TOTAL MEM
CACHED 873327085626 3331478.4 GB 30598875% of TOTAL MEM
SLAB 230128 898.9 MB 8% of TOTAL MEM
Fix after:
crash> kmem -i
PAGES TOTAL PERCENTAGE
TOTAL MEM 2854115 10.9 GB ----
FREE 169699 662.9 MB 5% of TOTAL MEM
USED 2684416 10.2 GB 94% of TOTAL MEM
SHARED 891094 3.4 GB 31% of TOTAL MEM
BUFFERS 329 1.3 MB 0% of TOTAL MEM
CACHED 1729018 6.6 GB 60% of TOTAL MEM
SLAB 230128 898.9 MB 8% of TOTAL MEM
I think crash tools without my patch, maybe miss some situation like this which symbol miss in kenrel vmlinux.
I think that using both branch of symbol_exist("nr_swapper_spaces") and symbol_exists("swapper_spaces") means to double check
the situation of all kinds of kernel and vmlinux.
It seen that bring my patch can deal with more unusual situation and make crash tool more compatible.
Thanks！
Best Regards
________________________________
From: HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx>
Sent: Friday, December 1, 2023 3:08:03 PM
To: 薛国伦; devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Lianbo Jiang
Subject: Re: [External Mail]Re: [Crash-utility] [BUG FIXED]fix bug of CACHED in kmem -i show memory
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On 2023/11/30 22:05, 薛国伦 wrote:
> Hi kazu:
>
>
> 1. I found that vmlinux of kernel-6.1 did not have symbol nr_swapper_spaces but only have swapper_spaces
>
> Also check in GKI vmlinux, can not find nr_swapper_spaces
Hmm, upstream kernel 6.1 has it.
$ git show v6.1:mm/swap_state.c
struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
>
> It may have some problem in symbol of nr_swapper_spaces
>
>
> 2. I think that crash tools will check nr_swapper_spaces first and then check *swapper_spaces, swaper_space[] last.
>
> so first check nr_swapper_spaces not found, crash tool can use *swapper_spaces to enhance compatibility.
>
> The patch i send can resolve this situation which nr_swapper_spaces symbols can not found.
But I cannot determine whether your patch is correct and should be
applied, without kernel patches or the cause of no nr_swapper_spaces.
Could you please find the information (e.g. links) of the related kernel
patches?
Thanks,
Kazu
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From 1ba60970180866f1bdb2ef8cacf6f600e5dad4ef Mon Sep 17 00:00:00 2001
From: Johan Erlandsson <johan.erlandsson@xxxxxxxx>
Date: Wed, 19 Apr 2023 11:26:04 +0200
Subject: [PATCH] read swapcache usage when nr_swapper_spaces isn't available
In 5.12 the following change was introduced:
b6038942480e574c697ea1a80019bbe586c1d654
Then the variable 'nr_swapper_spaces' is not read (unless
CONFIG_DEBUG_VM=y). In GKI builds this variable is then optimized
out. But the same change provided a new way to obtain the same
information, using NR_SWAPCACHE.
---
memory.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/memory.c b/memory.c
index 791194a..439e6e3 100644
--- a/memory.c
+++ b/memory.c
@@ -8609,7 +8609,8 @@ dump_kmeminfo(void)
char *swapper_space = GETBUF(SIZE(address_space));
swapper_space_nrpages = 0;
- if (symbol_exists("nr_swapper_spaces") &&
+ if (dump_vm_stat("NR_SWAPCACHE", &swapper_space_nrpages, 0)) {
+ } else if (symbol_exists("nr_swapper_spaces") &&
(len = get_array_length("nr_swapper_spaces",
NULL, 0))) {
char *nr_swapper_space =
--
2.42.0
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